Field of the Invention
The present invention relates to a radiation measurement apparatus which obtains information on a position on which a radiation ray is incident and a radiation measurement method.
Description of the Related Art
In an array-type gamma-ray (γ-ray) detector including a plurality of pixels, signals may be detected in a number of pixels of the detector since a γ-ray reaches neighboring pixels in a case where Compton scattering is generated in a pixel on which the γ-ray is incident. In this case, it is difficult to determine a position (pixel) on which the γ-ray is externally incident. In general, a position on which a γ-ray is incident is determined by various methods. In a case where all energy of a detected γ-ray is equal to or smaller than 511 keV, a maximum value of an energy detected in a pixel in which the Compton scattering is generated once is equal to or smaller than half of that of the incident γ-ray. Therefore, in a case where signals are detected in two pixels, one of the pixels in which a lower energy is detected, that is, one of the pixels in which the Compton scattering is generated, is judged as a pixel on which the γ-ray is incident. An example is described in U.S. Pat. No. 6,512,232.
However, depending on an energy of an incident γ-ray, a detected energy of a pixel in which the Compton scattering is generated becomes larger than a detected energy of a pixel in which photoelectric absorption is generated. Furthermore, in a case where the Compton scattering is generated a plurality of times, signals are detected in three or more pixels.